1. Field of the Invention
The invention relates to the field of packaging materials for large cylindrical objects, such as coils of aluminum and steel and spools of cable.
2. Description of Related Art
A number of problems exist in the transportation and storage of large, generally cylindrical materials such as coils of metal and spools of cable. The cylindrical units are large, typically on the order of 48 to 78 inches in diameter, and may weigh in excess of ten thousand pounds. Moreover, the units are subject to rough handling in transportation and extended periods of storage under unfavorable conditions, typically outdoors exposed to a wide temperature range and precipitation. Packaging of such units in individual wooden boxes provides a degree of protection, but is undesirable due to the addition of weight and volume to the individual units and failure to provide thermal protection against "greenhouse" condensation of moisture in contact with the packaged material.
Where spools of cable are concerned, the practice has been to nail boards called "lags" on the outside of the spool. This is a labor intensive operation which adds considerable weight to the spool and only limited protection against the elements.
It has been proposed to wrap cylindrical units with various materials as protection. For example, U.S. Pat. No. 3,660,958 proposes wrapping rolls of paper or the like with a corrugated material in order to provide basic physical protection against rough handling during transportation. While corrugated cardboard would provide a basic degree of protection, it would not be suitable for units left exposed to the elements, and in fact, U.S. Pat. No. 3,660,958 discloses rolls wrapped with corrugated cardboard only over a fraction of their length, so that a substantial portion of the length of the roll is unprotected.
It has also been proposed to wrap cylindrical materials in plastics, but the typical plastic wrap provides only a limited degree of protection against rough handling Moreover, such plastic wraps do not provide the degree of thermal insulation necessary to avoid substantial condensation between the wrap and a coil, condensation which can cause deterioration of the wrapped material, for example, steel and aluminum coils.
An improved wrapping material for objects is disclosed in U.S. Pat. No. 3,668,049. The '049 patent is directed to a laminated packing material having two outer layers and an intermediate array of spaced, parallel, stiffening rib members secured to the outer layers. The material disclosed in the '049 patent is sold commercially by Swedeboard Inc. under the trademark LAMIFLEX and comprises a plastic or polyethylene coated outer layer with a polyethylene coated kraft paper inner skin and stiffening rib members made from wood fiber composite. This material is advantageous in that it is highly flexible in one direction, perpendicular to the stiffening rib members, but inflexible in the direction parallel to the rib members.
It has accordingly been suggested to use this packing material for wrapping large coils of metal and spools of cable. The material has proved satisfactory from the standpoint of rough handling, but the laminate deteriorates when exposed to the elements because the edges of the wood fiber ribs absorb moisture and serve as a wicking material to carry moisture throughout the entire wrapping. Also, tears in the material permit exposure of the wood fibers to moisture and the wicking effect to take place. Further, this material does not prevent condensation of moisture within the wrapping.